[Test2Test]

So the thing is, I remember one anime from childhood of which I don't remember anything. But all I remember is one thing, in one episode, there was this character (I don't even know if he's main character or not), that character, in past time has experience a genocide/mass killing of his friends/family (I don't remember properly), and all that killing happened after a symbol appeared on them.
Years later, he got that symbol on him as well, and he becomes extremely powerful. Also if I remember correctly, one of his powers was to shoot energy ball like stuff. And if I'm correct, he look/wears purple.
I know this is an absurd description, but that's all I really know about that great episode.

[0101truck]

So the thing is, I remember one anime from childhood of which I don't remember anything. But all I remember is one thing, in one episode, there was this character (I don't even know if he's main character or not), that character, in past time has experience a genocide/mass killing of his friends/family (I don't remember properly), and all that killing happened after a symbol appeared on them.
Years later, he got that symbol on him as well, and he becomes extremely powerful. Also if I remember correctly, one of his powers was to shoot energy ball like stuff. And if I'm correct, he look/wears purple.
I know this is an absurd description, but that's all I really know about that great episode.

I think you could be referring to Tokyo Majin, I watched it a long time ago so my memory might be incorrect

[abd0804]

Maybe you're talking about "Death Parade"

[NortherlyShout]

Even with a limited description, I watched this Code Geass a long time ago and could be a possiblity. While the symbol you remember might not be an exact match, Lelouch's Geass manifests as a red sigil over his left eye. There are also instances of mass killings throughout the series.